Note: Descriptions are shown in the official language in which they were submitted.
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WO 00/16643
Encapsulated perfumes and/or aromas having a specific release behaviour
The present invention relates to encapsulated aromas and/or perfumes and to
processes for their production.
Aromas (flavouring matters) and perfumes are complex liquid mixtures of
volatile
components. During the production and preparation of aromatized foods and
perfumed products, there is the necessity for controlling the release of
aromas or
perfumes in order to avoid losses.
Especially in the case of water-containing foods which are ultra-heated,
protection of
the aroma is a technological challenge. In this case, significant aroma losses
occur
owing to the volatility of the aroma components on heating. In addition, in
the case
of aroma compositions, due to the differing loss rates of the individual
components,
shifts in aroma profile can occur. The transfer of the aroma into the liquid
during the
high-temperature phase in a food processing process must therefore be avoided.
For
this purpose encapsulation of the aroma is suitable. This aroma capsule should
then
ideally dissolve in a controlled manner during the cooling phase and thus also
release
the aroma in a controlled manner.
The application of coatings to particles to establish the solubility behaviour
or release
behaviour and for protecting encapsulated substances is known. Jackson and
Lee, in
their review article "Microencapsulation and the Food Industry" (Lebensm.-
Wiss.u.-
Technol. 24, 289-297 (1991)) enumerate a great number of suitable coating
materials, including fats, waxes, hydrocolloids, for example including
modified
celluloses, and proteins.
WO 97/16078 describes a process only of aroma substances and perfumes which
can
be encased by a protective skin. As possible casing, inter alia, modified
cellulose is
also mentioned. The granules themselves are inhomogeneous and comprise a
support
material and an aroma enclosed in a film-forming agent. The propose of this
application is to produce granules as free as possible from dust. The
resultant
particles have an irregular shape and an uncontrollable constituent release
behaviour.
A reduction in the release rate of encapsulated aromas having a hydrophilic
matrix in
aqueous systems is customarily achieved by applying coatings of hydrophobic
substances, for example fats or waxes, and also of gel-forming proteins or
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hydrocolloids. However, for clear aqueous foods, fats or waxes are unsuitable,
since
visually unacceptable deposits in the food form when they are used.
Although hydrocolloid gels are hydrophilic, that is to say they are
colloidally soluble
in aqueous systems, the hydration and solubility of the gel increases in many
of these
systems constantly with increasing temperature, however. Aroma protection is
then
lowest precisely at high temperatures.
In contrast, certain modified celluloses are distinguished by reversible
formation of a
solid gel in water at elevated temperatures, which is unique in the
hydrocolloid
group. The viscosity of these gels increases greatly at high temperatures
(above the
characteristic flocculation point, that is to say the temperature from which
solid,
high-viscosity gels are formed), and then decreases again on cooling. The
reversibility of gel formation also significantly distinguishes the modified
celluloses
from the behaviour of protein gels which, although they can also gel at high
temperature, their gels do not redissolve on cooling.
This viscosity and temperature behaviour above the flocculation point, which
is the
inverse of that of other gel systems, and the reversibility of gel formation
of certain
modified celluloses is termed "reversible thermal gelation" (Edible Films and
Coatings: A Review, Food Technology, December 1986, 47-59).
The utilization of the reversible thermogelation of methyl cellulose or
hydroxypropyl
cellulose in the use as protected matrix for temperature-sensitive substances
is known
per se.
In WO 92/11084, methyl cellulose is used in a capsule matrix for the sweetener
aspartame which is unstable in water-containing media at high temperatures.
The
stability of the sweetener in bakery products can thus be increased.
WO 98/49910 describes the encapsulation of foodstuffs and other materials,
these
materials first being encased with a hydrophobic film and then with a layer
which
has a temperature-dependent reversible solution behaviour. This layer can
consist of
cellulose derivatives or other polymers. The inner hydrophobic film consists,
for
example, of fats, paraffin or water. It is also possible that an outer
hydrophobic layer
is further placed around the polymeric layer having reversible solution
behaviour.
The encapsulated material can be of variable size and can be present from the
food
itself or in tablet form. The inner layer can also be present in the
encapsulated
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material (hybrid system). A disadvantage of this system is the hydrophobic
layer,
which in an aqueous system deposits on the surface in an unwanted manner.
The object of the present invention was, in the production of aromatized,
water-
s containing foods which pass through a heating process, to control
effectively the
aroma release. The release rate in the cooling phase should be specifically
controllable in a time- and temperature-dependent manner up to complete cold
water
solubility. In addition, the release rates for different aroma components
should be
approximately equal, in order to prevent unwanted shifting of the flavour
profile.
Aroma losses are to be decreased by delaying the release at high temperatures.
Encapsulated aromas and/or perfumes have been found which are characterized in
that they consist of hydrophilic solid particles in which the aromas and/or
perfumes
are enclosed and which are encased with or comprise modified cellulose, this
having
reversible gel formation on temperature increase.
The inventive use of certain modified celluloses for the protection and
inversely
temperature/time-controlled release of encapsulated aromas and/or perfumes in
hot
aqueous systems was surprising.
The cellulose for the inventively encapsulated aromas and/or perfumes forms a
film
which has a high viscosity precisely at high temperatures in aqueous media and
is a
diffusion barrier for aroma substances. During gradual subsequent cooling, the
cellulose gel layer has increased swellability, controllable viscosity
decrease as far as
complete residue-free solubility. The aroma can, as a result, be released in a
time/temperature-dependent manner and linearly. The mode of functioning of the
coating (delay rate) can be optimally matched to the respective application
requirements.
The modified cellulose forms a casing of the aroma particles and/or perfume
particles. The diffusion of the aroma substances or perfumes through the
casing layer
and thus their release can be controlled via the selection of the cellulose
having the
specific flocculation point and via the thickness of the casing layer.
The inventive encapsulated aromas and/or perfumes can comprise 1 to 50% by
weight, preferably 2 to 20°Io by weight, particularly preferably 5 to
10% by weight,
of modified cellulose. The respective amount of cellulose determines the layer
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thickness and controls the release rates for the aromas and/or perfumes, the
more
slowly the release taking place the higher the cellulose content.
Modified celluloses for the inventive encapsulated aromas and/or perfumes are
taken
to mean modified celluloses which can form thermally reversible gels.
Particular
preference is given here to methyl cellulose, hydroxypropyl cellulose,
hydroxypropyl
methyl cellulose, ethyl methyl cellulose, ethyl cellulose or mixtures thereof.
Reversible thermal gelation cannot occur with all substances which are
summarized
under the term "modified celluloses". Gels other than the inventive "modified
celluloses", for example carboxymethyl cellulose, do not behave in the desired
manner.
Hydrophilic aroma particles and/or perfume particles are composed of an aroma
mixture and/or a perfume mixture and a hydrophilic support (for example gum
arabic
or dextrins, such as maltodextrin) which is known per se.
It is also possible to add other substances, for example vitamins,
microorganisms,
edible acids or colours.
For the present invention it is essential that no further layers are necessary
to protect
the core.
The invention also relates to a process for producing encapsulated aromas
and/or
perfumes, in which the aroma particles and/or perfume particles are provided
with a
coating. This process is characterized in that the coating comprises a
modified
cellulose with which reversible gelation occurs with temperature increase.
The inventive production process produces encapsulated aromas and/or perfumes
of
the abovedescribed type having the advantages mentioned there. These
encapsulated
aromas and/or perfumes can comprise after their manufacture 1 to 50% by
weight,
preferably 2 to 20% by weight, particularly preferably 5 to 10% by weight, of
modified cellulose. Modified celluloses which may be mentioned are in
particular
methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose,
ethyl
methyl cellulose, ethyl cellulose or mixtures.
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Preferably, the aroma particles and/or perfume particles as serving as core
are
produced by fluidized-bed spray granulation. The production of these cores is
known
per se.
The particles have a diameter of 10 to 5000 ~Cm, preferably 200 to 2000 ~,m.
EP 070 719 describes the production of aroma particles and/or perfume
particles in a
fluidized bed which is operated batchwise. In this case an aqueous emulsion of
the
aromas and/or perfumes to be granulated and suitable support materials are
sprayed
into a fluidized bed which consists of particles vortexed by air. The
particles then act
as seeds for the formation of granules.
EP 0 163 836 describes an apparatus for producing granules by a continuously
operated fluidized bed. The generation of granules and the selected discharge
on
reaching the desired particle size proceed simultaneously and continuously.
WO 97/16078 describes the production of aroma particles and/or perfume
particles in
a fluidized-bed rotor granulator which is operated batchwise. Via a rotating
base
plate, the rotor granulator produces a fluidization of the fluid bed present
in it, so that
less air is required for its fluidization.
According to the invention preference is given to the continuous mode of
producing
the particles in an apparatus according to EP 0 163 836.
After the fluidized-bed spray granulation step, by spraying on a solution
which
comprises water and a modified cellulose, a coating film having uniform
defined
layer thickness is applied to the aroma particles and/or perfume particles
containing
the aromas or perfumes encapsulated therein. For this purpose, apparatuses
which are
known per se, preferably fluidized-bed apparatuses (top-spray coaters, bottom-
spray
coaters, Wurster coaters) are used.
As solvents for the spray solution there can be used, for example, water or
water/ethanol mixtures. The said modified celluloses are made up in the spray
solution at a concentration between 0% and 25%, preferably between 1 % and
15%.
Preferably, for applying coatings, modified celluloses are selected which have
a
degree of etherification which give only a low viscosity to the spray
solution.
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The suitable feed air temperatures during coating in the fluidized bed are
between
SO°C and 140°C. The suitable exhaust air temperatures during
coating in the
fluidized bed are between 30°C and 100°C.
The layer thickness is 1 to 200 ~Cm, preferably 2 to 100 ~Cm, in particular
preferably 5
to 50 p, m.
The layer thickness is set by the amount of coating solution sprayed on.
Depending on the application, other substances or else mixtures of substances,
for
example other hydrocolloids, fats, waxes, sugars or else plasticizers, for
example
polyethylene glycol or other customary additives, for example food colours,
can be
added to the spray solution.
In an alternative embodiment of the present invention, the aroma particles
and/or
perfume particles are encased not by a unitary casing, but by impregnation of
the
particles with the modified cellulose.
Suitable encapsulated substances are all aroma and/or perfume mixtures which
are
used in industry, and also individual aroma components and/or perfume
components.
The invention in addition relates to a process for enriching foods with aromas
or for
producing perfumed consumer articles, for example detergents. This process is
characterized in that the above described encapsulated aromas and/or perfumes
are
added to the foods or the consumer articles.
Examples which may be mentioned are infusion bag tea, instant sauce powder,
prepared sauce, pasteurized beverages, chewing sweets, wafers, detergents.
Preferably, the foods, during or after the addition of the inventive
encapsulated
aromas and/or perfumes are heated to a temperature above the flocculation
point of
the modified cellulose and are then cooled.
By means of the particular release behaviour of the inventive aromas, new
qualities
of the foods can be achieved. Thus, for example, heating is possible without
an
excessive aroma loss occurnng. During cooling of the foods, vice versa, the
desired
and defined release of the aromas occurs, which can be controlled in its time
course
by the type of encapsulation. Since the different individual aroma components
are
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released at the same rate, and their weight ratio to one another therefore
remains
constant, no unwanted shifts in aroma profile occur either.
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Examples
The invention is described in more detail below with reference to example
embodiments with associated figures.
Figure 1 shows the aroma release of encapsulated aromas with and without a
coating
of modified cellulose.
Figure 2 shows the release of different aroma components.
Example 1
Production of capsules having a release rate of 50% per minute at temperatures
above 60°C
A solution of 2.0% by weight of low-viscosity methyl cellulose (viscosity of a
2%
strength aqueous solution at 20°C: 400 cP) in water is produced. The
flocculation
point of this methyl cellulose is above 50°C.
In a fluidized-bed apparatus of the type shown in EP 0 163 836 (having the
following
features: diameter of gas distributor plate: 225 mm, spray nozzle: two-
component
nozzle, classifying discharge: zig-zag sifter, filter: internal bag filter)
particles which
comprise an encapsulated model aroma mixture (consisting of ethyl butyrate:
limonene: phenylethyl alcohol, 1:1:1) coated with methyl cellulose. By raising
the
classifying gas rate to 20 kg/h at 30°C no material is discharged, that
is to say coating
takes place batchwise. For this operation 480 g of aroma particles are
introduced as
initial bed charge. The methyl cellulose solution is sprayed into the
fluidized-bed
granulator at a temperature of 22°C. The temperature of the atomizing
gas is 30°C.
To fluidize the bed contents, nitrogen is blown in at a rate of 120 kg/h. The
inlet
temperature of the fluidizing gas is 140°C. The temperature of the
exhaust gas is
81 °C. Free-flowing granules are obtained. The solid particles are
round. The thin,
highly uniform methyl cellulose coating is 5% by weight, based on the granule
weight.
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Example 2
Production of capsules having a release rate of 10°lo per minute at
temperatures
above 60-C
A solution of 2.0% by weight of a low-viscosity methyl cellulose (viscosity of
a 2%
strength aqueous solution at 20°C: 400 cP) in water is produced. The
flocculation
point of this methyl cellulose is above 50°C.
A coating of methyl cellulose is applied to aroma particles which comprise an
encapsulated model aroma mixture (consisting of ethyl butyrate: limonene:
phenylethyl alcohol, 1:1:1) as in Example 1, but twice as much casing is
applied. For
this, coating must be carned out for correspondingly longer.
The methyl cellulose coating is 10% by weight, based on the granule weight.
The functioning of the coating material is described by the diagrams in
Figures 1 and
2. Figure 1 shows the delay of aroma release during brewing with hot (boiling)
water
due to a coating of methyl cellulose (the encapsulated aromas were produced in
accordance with Examples 1 and 2).
The time axis on the x-axis extends from 0 to 600 seconds. On the left y-axis
is
plotted the percentage of aroma released (from 0 to 100%) and on the right y-
axis,
the respective process temperature (from 0°C to 100°C) can be
read off by the
associated falling line.
Conventional aroma particles without casing (continuous, steeply increasing
line)
show rapid release of the aromas. Even after one minute, virtually the entire
aroma
has been released.
In contrast, the inventive encapsulated aromas release their contents
significantly
slower. The release rate may be controlled in this case by the methyl
cellulose
content. At a content of 10% methyl cellulose (dotted curve) it is
substantially lower
than at a 5% methyl cellulose content (dashed curve).
Figure 2, for the same process, shows the release curves for two different
aroma
components (dotted and continuous lines). These run almost overlapping. That
is to
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say that the components are released at the same rate, so that an undesired
shift in the
flavour profile does not occur.
Example 3
Production of capsules containing strawberry aroma
A solution of 2.0% by weight of a low-viscosity methyl cellulose (viscosity of
a 2%
strength aqueous solution at 20°C: 400 cP) in water is produced. The
flocculation
point of this methyl cellulose is above 50°C.
A coating of methyl cellulose is applied to aroma particles which comprise an
encapsulated strawberry aroma in a fluidized-bed apparatus of the GPCG 3 type
from
Glatt having the following features:
Diameter of gas-distributor plate: 150 mm,
Spray nozzle: Two-component nozzle,
Filter: Internal bag filter,
Fluidizing gas inlet temperature: 100°C,
Exhaust air temperature: 60°C,
Atomizing gas temperature: 22°C,
Fluidizing gas rate: 50 kg/h.
The methyl cellulose coating is 10% by weight, based on the granule weight.
4. Application examples
4.1. Tea in infusion bays
To tea in bags are added aroma particles having strawberry aroma encapsulated
therein, which are furnished with methyl cellulose coating, and aroma
particles
without methyl cellulose coating which comprise the same strawberry aroma.
Advantages:
After infusion of the aromatized tea bags, the following are obtained
- both a strong immediate aroma impact which is perceived by odour
(orthonasally) and flavour (retronasally),
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- and a persistent aromatizing (intensity, aroma profile) of the beverage,
which
is independent of brewing time over a brewing time of a plurality of minutes.
The losses which occur on infusion with boiling water via transfer of the
aroma
substances released from the uncoated aroma particles into the water vapour
are
compensated for in succession with advancing cooling of the tea by gradual and
linear release of the aroma from the coated aroma or perfume particles.
4.2. Instant sauce
An instant sauce powder is aromatized with white wine aroma granules which are
coated with methyl cellulose. During the preparation, the sauce is heated with
water
in the pot to above boiling temperature for at least 5 minutes.
Advantages:
The loss of volatile aroma components during heating is reduced. Full aroma
action
during consumption.
4.3. Prepared sauce
A pasta sauce is aromatized with tomato aroma particles which are coated with
methyl cellulose. For preservation purposes, the sauce is heated to
80°C to 100°C for
10 minutes and then cooled in the closed packaging.
Advantages:
The loss of volatile aroma components during heating is reduced. Complete
release
of aroma does not take place until cooling of the sauce in the closed vessel.
4.4. Pasteurized drink
During the heat-treatment step in a soft drink production process for
preservation,
granules containing encapsulated ethyl butyrate are added which are coated
with a
film of methyl cellulose.
Advantages:
Improvement of the aroma profile by protecting the volatile ethyl butyrate
during the
heating step and subsequent complete release of the ethyl butyrate during the
cooling
process in the closed vessel. The coating leaves no residue behind in the
final drink.
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4.5 Chewing sweets
Red-dyed aroma granules containing raspberry aroma encapsulated therein and
methyl cellulose coating is added prior to shaping at 1% into the hot
(120°C)
chewing sweet mass which comprises sucrose, water, glucose syrup, fat,
fondant,
gelatin, citric acid and an emulsifier, and the mixture is then cooled and
aerated.
Advantages:
- The granules do not dissolve during the production process, so that a visual
effect can be achieved via the conspicuous granules in the end product.
- Low aroma losses occur during the processing operation.
The aroma is present in the matrix localized at few points and does not
migrate. As a
result, a special sensory effect is achieved (hot spots). The surrounding
chewing
sweet mass can be aromatized with another liquid aroma, whereby a double
sensory
effect can be achieved.
4.6. Detergent
Granules which comprise an encapsulated perfume combination (lily of the
valley
fragrance) and which is furnished with a coating of modified cellulose is used
to
perfume washing powder.
Advantage:
The perfume dose in the detergent can be reduced. Loss of perfuming during
washing of clothes via leaching with the washing water is minimized, since the
aroma particles adhere to the clothing fibres. The encapsulated perfume is
protected
in particular at high washing temperatures.
4.7. Ice cream wafers
Yellow-dyed aroma granules having lemon aroma encapsulated therein and a 5%
strength methyl cellulose coating are added at a dose of 2% by weight to a
dough
mixture for manufacturing ice cream wafers. This dough mixture consists of
water
(45%), wheat flour (35%), sucrose (15%), ground nut oil, lecithin, salt. The
dough
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containing the aroma granules is then poured out thinly onto a 250°C
wafer iron and
baked for 1.5 minutes. The wafers are then rolled up to form cones.
Advantages over uncoated aroma granules:
The aroma granules are retained during the baking process and only small
losses of
the encapsulated volatile lemon aroma occur. The aroma is not released until
during
consumption, mechanically by chewing.
Due to the localization of the aroma at individual points in the wafer, a
special
sensory effect can be achieved.
A visual effect can be achieved by the retention of the conspicuously dyed
granules.
